Without a spectra, and based on the cost, I would assume that to be a Zwb2 filter.
There has been lots of discussion here about those filters.
When I decided to get a convoy, even though more expensive up front I still think the U340 filter is the best match. You are guaranteed to eliminate all visible. Without that, what would be the point of adding a filter.

Based on the graph they show, see how the transmission crosses the 400nm line into the visible range, ever so slightly, but nonetheless the whole idea of filtering the Nichia LED (used in the Convoy) is to cleanly cut the transmission below 400nm.
This would then be ZWB2, as Da Bateman suggested, the very cheap Chinese imitation of Schott UG1 and Hoya U-360.
Many people think using UG1 or U-360 is better for 365nm, however those don't cut as cleanly below 400nm,
that is why when you filter a UV 365nm torch/LED you should really use U-340 or UG11, because those cut transmission cleanly below 400nm.

First of all, I don't trust the charts I see for the cheap Chinese filter glass.
It is possible that filtering the Nichia 365nm LED with either U-340 or U-360 would probably be cutting some of the blue leak,
however, technically if you are going to go to the trouble of filtering the torch, then it should be filtered below 400nm completely.
I have seen on other forums people talking about filtering with 360nm glass (UG1, U-360, 'ZWB2'), but those don't cut below 400nm.
When I compare the graphs, I don't see much benefit of using 360nm glass rather than 340nm glass (UG11, U-340, 'ZWB1').
Personally, I would use a 340nm glass.

So from that it looks like 2mm UG11 takes you down 2+ orders of magnitude, which presumably is good enough. The ZWB seems to have 5% transmission at 400nm, which 1.3 orders. (Even if you trust the chart...)